Effects of addition of nutritionally improved straw in dairy cow diets at 2 starch levels.

The objective of this experiment was to explore the effects of different dietary neutral detergent fiber sources within diets of high-producing dairy cattle with low or high starch concentrations on milk yield and composition, dry matter intake (DMI), total-tract digestibility, nitrogen (N) partitioning, and rumen function and health. Holstein-Friesian cows in early- to mid-lactation (n = 12; 666 ± 67 kg of body weight at the start of the experiment) and dry cannulated Holstein-Frisian cows (n = 4; 878 ± 67 kg of body weight at the start of the experiment) were used in multiple 4 × 4 Latin square design experiment and were offered 4 different diets. The treatments were 50:50 forage-to-concentrate diets within a total mixed ration (TMR) consisting, on a dry matter (DM) basis, of 42.4% grass silage as the main forage, 7.6% chopped untreated wheat straw, or sodium hydroxide (NaOH) wheat straw pellets, known as nutritionally improved straw (NIS), and 50.0% of 1 of 2 different concentrates with low or high starch level (TMR starch level of 16.0 vs. 24.0% of DM, respectively). Four experimental periods were used, each consisting of a 21-d adaptation period and 7 d of sampling. Dry matter intake and milk yield were both affected by the type of straw included in the diet. A 1.6 kg/d higher DMI was seen when NIS was fed compared with untreated straw, resulting in a 1.7 kg/d higher milk yield. Milk protein concentration was affected by straw type and starch level, and it was 4 and 3% higher when NIS and high-starch diets were fed, respectively. Diets with NIS were more positively effective when fed with low levels of starch. These results illustrate that feeding NIS to high-producing lactating dairy cows fed low or high starch concentrations has a positive effect on performance.

Lactation and body composition responses to fat and protein supplies during the dry period in under-conditioned dairy cows.

An experiment was designed to study the effect of precalving supplementation with protein (Pr) and rumen-inert fat (F) on body composition and subsequent milk production and composition. Forty Holstein-Friesian dairy cows were allocated to 1 of 4 dietary treatments in the dry period (DP) based on a first-cut ryegrass silage, with 6 mature (in their third or greater pregnancy) and 4 young (in their second pregnancy) cows per treatment. These were low Pr, low F (silage alone); low Pr, high F (silage with 10% rumen-inert fat, mixed on a dry matter basis); high Pr, low F [silage with 5% high-protein corn gluten meal (CGM)]; and high Pr, high F (silage with 5% CGM and 10% rumen-inert fat). All the diets were individually offered ad libitum and dry matter intake (DMI) was recorded daily during the DP. After calving, all cows received ryegrass silage plus 8 kg/d of a commercial dairy concentrate. During the DP, DMI was higher for mature than for young cows. All animals recovered body condition score (0.13 units/wk, 1-5 scale), reaching a maximum score of 2.4 some days before calving. Precalving maximum muscle longissimus dorsi (LD) depth was greater for mature (47.5 mm) than for young cows (45.7 mm), and milk fat concentration was also higher for mature than for young cows (40.2 and 39.0 g/kg, respectively). Supplementation with CGM increased maximum LD depth (from 45.9 to 47.6 mm), calf birth weight (low Pr = 43.2, high Pr = 46.3 kg), and milk crude protein concentration (from 30.8 to 31.6 g/kg). Fat supplementation in the DP of the mature cows increased maximum back fat depth (from 3.6 to 4.5 mm), milk yield (low F = 26.3, high F = 28.7 kg/d), and Pr yields (low F = 837, high F = 899 g/d). Inclusion of F in the DP diets reduced casein concentration in milk at wk 3 of lactation from 26.3 to 24.5 g/kg. Milk CP yield was also increased by CGM supplementation when compared within cows receiving F-supplemented silages (low Pr, high F = 832 g/d; high Pr, high F= 877 g/d). It can be concluded that CGM supplementation in the DP increased subsequent milk Pr concentration, but milk Pr yield increased only in those animals also receiving F supplementation. Dry period diet supplementation with F increased maximum back fat depth and milk and CP yields in the mature cows, and led to more LD muscle mobilization during early lactation. Second-calving cows had a lower DMI and milk fat concentration than mature cows.

Assessment of dietary ratios of red clover and corn silages on milk production and milk quality in dairy cows.

Twenty-four multiparous Holstein-Friesian dairy cows were used in a replicated 3×3 Latin square changeover design experiment to test the effects of changing from corn (Zea mays) silage to red clover (Trifolium pratense) silage in graded proportions on feed intakes, milk production, and whole-body N and P partitioning. Three dietary treatments with ad libitum access to 1 of 3 forage mixtures plus a standard allowance of 4kg/d dairy concentrates were offered. The 3 treatment forage mixtures were, on a dry matter (DM) basis: (1) R10: 90% corn silage and 10% red clover silage, (2) R50: 50% corn silage and 50% red clover silage, and (3) R90: 10% corn silage and 90% red clover silage. In each of 3 experimental periods, there were 21d for adaptation to diets, and 7d for measurements. Diet crude protein intakes increased, and starch intakes decreased, as the silage mixture changed from 90% corn to 90% red clover, although the highest forage DM intakes and milk yields were achieved on diet R50. Although milk fat yields were unaffected by diet, milk protein yields were highest with the R 0250 diet. Whole-body partitioning of N was measured in a subset of cows (n=9), and both the daily amount and proportion of N consumed that was excreted in feces and urine increased as the proportion of red clover silage in the diet increased. However, the apparent efficiency of utilization of feed N for milk protein production decreased from 0.33g/g for diet R10 to 0.25g/g for diet R90. The urinary excretion of purine derivatives (sum of allantoin and uric acid) tended to increase, suggesting greater flow of microbial protein from the rumen, as the proportion of red clover silage in the diet increased, and urinary creatinine excretion was affected by diet. Fecal shedding of E. coli was not affected by dietary treatment. In conclusion, even though microbial protein flow may have been greatest from the R 0450 diet, optimum feed intakes and milk yields were achieved on a diet that contained a 1:1 DM mixture of corn and red clover silages.

Measurement of rumen dry matter and neutral detergent fiber degradability of feeds by Fourier-transform infrared spectroscopy.

This study explored the potential of partial least squares (PLS) and Fourier-transform infrared spectroscopy (FTIR) to predict rumen dry matter (DM) and neutral detergent fiber (NDF) degradation parameters of a wide range of feeds for ruminants, as an alternative to the in situ method. In total, 663 samples comprising 80 different feed types were analyzed. In situ DM and NDF degradabilities were determined as follows: effective degradability (ED), rumen soluble fraction (A), degradable but not soluble fraction (B), rate of degradation of the B fraction (C), and indigestible NDF (iNDF). Infrared spectra of dry samples were collected by attenuated total reflectance from 600 to 4000cm(-1). Feeds were randomly classified into 2 subsets of samples with representation of all feed types; one subset was used to develop regression models using partial least squares, and the second subset was used to conduct an external validation of the models. This study indicated that universal models containing all feed types and specific models containing concentrate feeds could provide only a relatively poor estimation of in situ DM degradation parameters because of compositional heterogeneity. More research, such as a particle size distribution analysis, is required to determine whether this lack of accuracy was due to limitations of the FTIR approach, or simply due to methodological error associated with the in situ method. This latter hypothesis may explain the low accuracy observed in the prediction of degradation rates if there was physical leakage of fine particles from the mesh bags used during in situ studies. In contrast, much better predictions were obtained when models were developed for forage feeds alone. Models for forages led to accurate predictions of DMA, DMB, NDFED, and NDF concentration (R(2)=0.91, 0.89, 0.85, and 0.79, standard error = 4.34, 5.97, 4.59, and 4.41% of DM, respectively), and could be used for screening of DMED, NDFC, and iNDF. These models relied on certain regions of the FTIR spectrum (900-1150 and 1500-1700cm(-1)), which are mainly compatible with absorption of plant cell wall components, such as cellulose, pectin, lignin, cutin, and suberin, but also with nonstructural carbohydrates and certain active compounds. In conclusion, FTIR spectroscopy could be considered a low-cost alternative to in situ measurements in feed evaluation.

Estimation of feed crude protein concentration and rumen degradability by Fourier-transform infrared spectroscopy.

Currently, rapid methods are needed for feed analysis. This study examined the potential of Fourier-transform infrared (FTIR) spectroscopy to predict the nutritional value of a wide range of feeds for ruminants, as an alternative to the in situ technique. Moreover, we investigated whether universal equations could be developed that would allow the low-cost determination of crude protein (CP) concentrations and their kinetics of degradation into the rumen. Protein nutritional values of 663 samples comprising 80 different feed types were determined in terms of concentrations of CP, water-soluble CP (CP(WS)), total-tract mobile bag CP digestibility (CP(TTD)), and in situ CP degradability, including the rumen soluble fraction (CP(A)), the degradable but not soluble fraction (CP(B)), rate of CP(B) degradation (CP(C)), effective degradability (CP(ED)), and potential degradability (CPPD). Infrared spectra of dry samples were collected by attenuated total reflectance from 4000 to 600 cm(-1). Models were developed by partial least squares (PLS) regression in a randomly selected subset of samples, and the precision of the equations was confirmed by using an external validation set. Analysis by FTIR spectroscopy was sufficiently sensitive to allow the accurate prediction of sample CP concentration (R(2)=0.92) and to classify feeds according to their CPWS concentrations using universal models (R(2)=0.78) that included all sample types. Moreover, substantial improvements in predictions were observed when samples were subdivided in groups. Models for forages led to accurate predictions of CP(WS) and fractions CP(A) and CP(B) (R(2)>0.83), whereas models for CP(TTD) and CP(ED) could be used for screening purposes (R(2)>0.67). This study showed that models for protein-rich concentrates alone could also be used for screening according to the feed concentrations of CP(WS), CP(TTD), CP(ED), CP(A), and CP(B), but models for energy-rich concentrates gave relatively poor predictions. The general difficulty observed in predicting CP(C) is because of a low correlation between FTIR spectra and the kinetics of CP degradation, which may be the result of large variation in the reference method (i.e., in situ degradation studies) and perhaps also because of the presence of compounds that can modify the CP degradation pattern in the rumen. In conclusion, FTIR spectroscopy should be considered as a low-cost alternative in the feed evaluation industry.

Effects of the addition of non-fibre carbohydrates with different rumen degradation rates in dairy cow high-forage diets using the Rumen Simulation Technique.

Nutrient synchronisation of protein and carbohydrates is a promising practice to improve ruminal nutrient utilisation. However, dietary sources supplying these nutrients can vary in ruminal nutrient availability due to differing degradation rates, therefore potentially affecting utilisation of nitrogen (N). The effects of the addition of non-fibre carbohydrates (NFCs) with different rumen degradation rates in high-forage diets on ruminal fermentation, efficiency and microbial flow were investigated in vitro using the Rumen Simulation Technique (RUSITEC). Four diets were tested: control with 100% ryegrass silage (GRS) and substitution of 20% on a DM basis of ryegrass silage with corn grain (CORN), processed corn (OZ) or sucrose (SUC). The four diets were assigned to 16 vessels in two sets of RUSITEC apparatuses in a randomised block design over a 17 d experimental trial; 10 d consisted of adaptation and 7 d for sample collection. Rumen fluid was collected from four rumen-cannulated dry Holstein-Friesian dairy cows and was treated without mixing. Then, rumen fluid from each cow was used to inoculate four vessels, and diet treatments were randomly allocated to each one. This was repeated for all cows resulting in 16 vessels. The inclusion of SUC in ryegrass silage diets improved DM and organic matter digestibility. The only diet to significantly lower ammonia-N concentration compared with GRS was SUC. The outflows of non-ammonia-N, microbial-N, and efficiency of microbial protein synthesis were not affected by diet type. However, the efficiency of nitrogen utilisation was improved by SUC compared with GRS. This indicates that the inclusion of an energy source with a high rumen degradation rate in high-forage diets improves rumen fermentation, digestibility, and N utilisation. Specifically, this effect was observed for the more readily available energy source, SUC, compared with the more slowly degradable NFC sources, CORN and OZ.

Effects of dietary protein concentration and balance of absorbable amino acids on productive responses of dairy cows fed corn silage-based diets.

A cyclical changeover design experiment (3-wk periods; 12-wk total) was conducted to evaluate whether improving the balance of absorbable AA would allow the feeding of less crude protein (CP) without compromising production, thereby reducing the potential environmental pollution from dairy farms. Sixteen multiparous Holstein cows were assigned to 1 of 8 dietary treatments as total mixed rations (TMR) containing [dry matter (DM) basis] 45% corn silage, 5% coarsely chopped wheat straw, and 50% concentrate mixture. The 8 treatments were formulated to differ in dietary CP (14 and 16%; DM basis) and in the balance of absorbable AA achieved by changing the main protein source (MPS) of the concentrate mixtures [replacing soybean meal (SBM) with corn byproducts (CBP), dried corn distillers grains (DDG), and some corn gluten meal], and by adding a mixture of rumen-protected Lys and Met (RPLM). Feeding lactating dairy cows corn silage-based diets with 16% CP promoted significantly higher DM intakes and milk yields, and lower feed N-use efficiency than feeding diets with 14% CP. Replacing SBM with CBP significantly increased milk yields and decreased milk fat and protein concentrations, but had no effect on the efficiency of conversion of feed N into milk N. With 16% CP diets, the addition of RPLM decreased feed N use efficiency. A significant effect was observed for the MPS × RPLM interaction on milk protein concentrations. Plasma Lys concentration was lower with diets based on CBP, and plasma Met increased with RPLM. We did not find clear benefits of RPLM in facilitating a reduction of dietary protein without loss of production.

Review: New feeds and new feeding systems in intensive and semi-intensive forage-fed ruminant livestock systems.

The contributions that ruminant livestock make to greenhouse gas and other pollutant emissions are well documented and of considerable policy and public concern. At the same time, livestock production continues to play an important role in providing nutrient-rich foodstuffs for many people, particularly in less developed countries. They also offer a means by which plants that cannot be digested by humans, e.g. grass, can be converted into human-edible protein. In this review, we consider opportunities to improve nutrient capture by ruminant livestock through new feeds and feeding systems concentrating on intensive and semi-intensive systems, which we define as those in which animals are given diets that are designed and managed to be used as efficiently as possible. We consider alternative metrics for quantifying efficiency, taking into account resource use at a range of scales. Mechanisms for improving the performance and efficiencies of both individual animals and production systems are highlighted. We then go on to map these to potential changes in feeds and feeding systems. Particular attention is given to improving nitrogen use efficiency and reducing enteric methane production. There is significant potential for the use of home-grown crops or novel feedstuffs such as insects and macroalgae to act as alternative sources of key amino acids and reduce reliance on unsustainably grown soybeans. We conclude by highlighting the extent to which climate change could impact forage-based livestock production and the need to begin work on developing appropriate adaptation strategies.

Evaluation of nitrogen excretion equations for ryegrass pasture-fed dairy cows.

Accurate and precise estimates of nitrogen (N) excretion in faeces and urine of dairy cattle may provide direct tools to improve N management and thus, to mitigate environmental pollution from dairy production. Empirical equations of N excretion have been evaluated for indoor dairy cattle but there is no evaluation for cows fed high proportions of fresh forage. Therefore, the objective of the current study was to evaluate N excretion equations with a unique data set of zero-grazing experiments. Through literature searches, 89 predictive equations were identified from 13 studies. An independent data set was developed from seven zero-grazing experiments with, in total, 55 dairy Holstein-Friesian cows. Models' performance was evaluated with statistics derived from a mixed-effect model and a simple regression analysis model. Squared sample correlation coefficients were used as indicators of precision and based on either the best linear unbiased predictions (R2BLUP) or model-predicted estimates (R2MDP) derived from the mixed model and simple regression analysis, respectively. The slope (ß0), the intercept (ß1) and the root mean square prediction error (RMSPEm%) were calculated with the mixed-effect model and used to assess accuracy. The root mean square prediction error (RMSPEsr%) and the decomposition of the mean square prediction error were calculated with the simple regression analysis and were used to estimate the error due to central tendency (mean bias), regression (systematic bias), and random variation. Concordance correlation coefficient (CCC) were also calculated with the simple regression analysis model and were used to simultaneously assess accuracy and precision. Considering both analysis models, results suggested that urinary N excretion (UN; R2MDP = 0.76, R2BLUP = 0.89, RMSPEm% = 17.2, CCC = 0.82), total manure N excretion (ManN; R2MDP = 0.83, R2BLUP = 0.90, RMSPEm% = 11.0, CCC = 0.84) and N apparently digested (NAD; R2MDP = 0.97, R2BLUP = 0.97, RMSPEm% = 5.3, CCC = 0.95) were closely related to N intake. Milk N secretion was better predicted using milk yield as a single independent variable (MilkN; R2MDP = 0.77, R2BLUP = 0.97, RMSPEm% = 6.0, CCC = 0.74). Additionally, DM intake was a good predictor of UN and ManN and dietary CP concentration of UN and ManN. Consequently, results suggest that several evaluated empirical equations can be used to make accurate and precise predictions concerning N excretion from dairy cows being fed on fresh forage.

Assessment of dietary ratios of red clover and grass silages on milk production and milk quality in dairy cows.

Twenty-four multiparous Holstein-Friesian dairy cows were used in a replicated 4 x 4 Latin square changeover design experiment to test the effects of changing from ryegrass (Lolium perenne) silage to red clover (Trifolium pratense) silage in graded proportions on feed intakes, milk production, milk organoleptic qualities, and whole-body nitrogen partitioning. Four dietary treatments, comprising ad libitum access to 1 of 4 forage mixtures plus a standard allowance of 4 kg/d dairy concentrates, were offered. The 4 forage mixtures were, on a dry matter (DM) basis: 1) 100% grass silage, 2) 66% grass silage: 34% red clover silage, 3) 34% grass silage: 66% red clover silage, and 4) 100% red clover silage. In each of 4 experimental periods, there were 21 d for adaptation to diets and 7 d for measurements. There was an increase in both DM intakes and milk yields as the proportion of red clover in the diet increased. However, the increase in milk yield was not as great as the increase in DM intake, so that the efficiency of milk production, in terms of yield (kg) of milk per kg of DM intake, decreased. The concentrations of protein, milk fat, and the shorter chain saturated fatty acids decreased, whereas C18 polyunsaturated fatty acids (PUFA) and long-chain PUFA (C20+) increased as the proportion of red clover in the diet increased. There was little effect of dietary treatment on the organoleptic qualities of milk as assessed by taste panel analysis. There were no effects on the aroma of milk, on aftertaste, or overall liking of the milk. Milk was thicker and creamier in color when cows were fed grass silage compared with red clover silage. The flavor of milk was largely unaffected by dietary treatment. In conclusion, increasing the proportion of red clover in the diet of dairy cows increased feed intakes and milk yields, decreased the concentration of fat and protein in milk, increased PUFA for healthiness, and had little effect on milk organoleptic characteristics.

Comparison of red clover and ryegrass silage for dry cows and influence on subsequent lactation performance.

The objective of this study was to investigate the use of red clover (RC) silage as a forage for dry dairy cows, primarily relative to its impact on tissue mobilization and repletion during the transition period and performance during the first 10 wk of lactation. Forty multiparous lactating Holstein-Friesian dairy cows were divided into 2 paired groups at 70 d before predicted calving dates; a subset (n = 8) of the cows were used for N and P balance measurements twice during the study. From the start of the experiment until 4 wk before predicted calving date all cows were offered ad libitum access to a ryegrass (RG) silage with no concentrate. At 4 wk before predicted calving date, one group of cows remained on the same diet, and the other group was changed to a diet of ad libitum access to RC silage. There was no difference in feed intakes, but CP intake was higher in cows fed RC silage, whereas ME intake was higher in cows fed RG silage. Cows fed RG silage gained more weight over the last 4 wk of the dry period (DP) than those fed RC silage, but there was no treatment effect on BCS. During the DP fecal N excretion was higher for cows fed RC silage, and there were no treatment differences in urine N excretion or overall N balance. At birth, calves from cows fed the RC silage were heavier. After calving, all cows were offered the same diet of ad libitum access to the same RG silage and a standard lactation concentrate. During the first 10 wk of lactation there was no difference in feed intake between the 2 previous treatment groups, and feed intake reached a maximum at approximately 4 wk of lactation. Cows on the RG treatment during the DP gained more longissimus dorsi muscle depth during the DP and retained it during early lactation. Mobilization of this muscle occurred before calving, indicating repartitioning of amino acids to other body tissues. There were no carryover effects of DP treatment on apparent partitioning of N from diet to milk, urine, or feces at wk 3 of lactation. Feeding RC silage during the DP had almost no impact on subsequent performance of dairy cows in early lactation, probably because the 2 silages were nutritionally very similar.

Normal ranges and temporal variation in plasma concentrations of L-lactate and free amino acids in adult sheep.

To determine baseline variation in blood plasma concentrations of free amino acids and l-lactate, samples were collected at a single time point from nine flocks of different breeds of ewes at a common physiological stage and monthly from one flock of crossbred mule ewes over a 12 month period. Significant differences were detected between time points in the concentrations of all plasma metabolites. With few exceptions prion protein genotype had no significant effect on the plasma metabolite concentrations measured.

Effect of scrapie incubation on the concentrations of plasma amino acids and L-lactate in infected lambs.

Three groups of two weeks old growing lambs differing in PrP genotype were orally inoculated with scrapie and maintained under defined conditions until disease endpoint. Plasma concentrations of free alanine and serine, but not L-lactate increased during the final 6 months of the disease. At the same time, plasma concentrations of several essential and non-essential free amino acids decreased linearly, indicating reduced feed intake and are consistent with, but occurring before establishment, of cachexia. These observations are consistent with those reported previously from studies on cattle infected with BSE and with the hypothesis that scrapie may effect peripheral tissue metabolism.

Apparent recovery of duodenal odd- and branched-chain fatty acids in milk of dairy cows.

This study compared flows of odd- and branched-chain fatty acids (OBCFA) at the duodenum with corresponding yields in milk. Four mid-lactation Holstein-Friesian dairy cows were offered 4 dietary treatments, based on different ratios of ryegrass silage and concentrates (80:20, 65:35, 50:50, and 35:65 on a dry matter basis), in a 4 x 4 Latin square design experiment with 4-wk periods. Samples of milk and duodenal digesta were collected during the final week of each period and analyzed for fatty acids. Biohydrogenation of linoleic and alpha-linolenic acids (C18:2 and C18:3) was extensive for all treatments, with a tendency to be lower for C18:3 with increased concentrate feeding. The proportion of duodenal flows of these fatty acids that appeared in milk declined with increasing concentrate feeding. There was little change in the yield of OBCFA in milk in response to increasing level of concentrate inclusion and no significant relationship with the yield of microbial protein at the duodenum. The efficiency of transfer of iso C15:0 and anteiso C15:0 from the duodenum to milk was similar to that for C18:3, with a reduced proportion transferred into milk at higher flows. Yields of C15:0, C17:0, and iso C17:0 in milk were higher than duodenal flows, confirming synthesis in animal tissues.

Changes in plasma metabolites and muscle glycogen are correlated to bovine spongiform encephalopathy in infected dairy cattle.

During the clinical phase of bovine spongiform encephalopathy (BSE), a significant decrease was observed in the ratio of muscle glycogen to plasma L-lactic acid concentrations in BSE infected field case and experimentally infected dairy cattle compared with healthy control cattle (P<0.001), this being due to changes in the concentration of both metabolites in the BSE infected cattle compared with the control group. Furthermore, the concentration of plasma alanine was significantly increased (P<0.05) in the infected animals. No significant difference was detected between these two groups in the ratio of hepatic glycogen to plasma lactate. We infer that BSE infected cattle exhibit signs of altered energy metabolism and when applied in conjunction with changes in other metabolite biomarkers these changes may be useful for discriminating BSE infected cattle from healthy cattle or those suffering with other disorders or diseases.

Characterization of the Microbiome along the Gastrointestinal Tract of Growing Turkeys.

The turkey microbiome is largely understudied, despite its relationship with bird health and growth, and the prevalence of human pathogens such as Campylobacter spp. In this study we investigated the microbiome within the small intestine (SI), caeca (C), large intestine (LI), and cloaca (CL) of turkeys at 6, 10, and 16 weeks of age. Eight turkeys were dissected within each age category and the contents of the SI, C, LI, and CL were harvested. 16S rDNA based QPCR was performed on all samples and samples for the four locations within three birds/age group were sequenced using ion torrent-based sequencing of the 16S rDNA. Sequencing data showed on a genus level, an abundance of Lactobacillus, Streptococcus, and Clostridium XI (38.2, 28.1, and 13.0% respectively) irrespective of location and age. The caeca exhibited the greatest microbiome diversity throughout the development of the turkey. PICRUSt data predicted an array of bacterial function, with most differences being apparent in the caeca of the turkeys as they matured. QPCR revealed that the caeca within 10 week old birds, contained the most Campylobacter spp. Understanding the microbial ecology of the turkey gastrointestinal tract is essential in terms of understanding production efficiency and in order to develop novel strategies for targeting Campylobacter spp.

Determining diet composition on complex swards using n-alkanes and long-chain fatty alcohols.

We conducted an experiment to quantify the accuracy of methods based on n-alkanes and long-chain fatty alcohols for determining the diet composition of animals grazing complex swards. We cut forage from two indigenous vegetation communities, a Molinia caerulea-dominated grassland and a Calluna vulgaris-dominated dwarf-shrub community, and offered it to mature ewes in different ratios in a zero-grazing experiment. Nine dietary categories were identified within the forage offered: Molinia caerulea, Festuca spp., Juncus effusus, Carex spp., Calluna vulgaris, Erica tetralix, Vaccinium myrtillus, and dead grass. Samples of each of these categories together with fecal samples from each individual animal were analyzed for n-alkane and long-chain fatty alcohol concentrations. We analyzed the data using optimization software to minimize the sum of squares differences in the proportional profiles of n-alkanes and fatty alcohols in the diet and feces. Different combinations of n-alkane and fatty alcohols were investigated to assess which gave the most accurate measures of diet composition from the fecal profile. The most accurate estimates were obtained using combinations of the n-alkanes C25, C29, C31, and C33 and the long-chain fatty alcohols 1-C24-ol, 1-C28-ol, and 1-C30-ol, and these gave values for Lin's concordance correlation coefficient between estimated and actual values of >0.98. Our results demonstrate that n-alkanes and long-chain fatty alcohols can be used to estimate several components within the diet of animals grazing complex swards. Diet composition information obtained using this methodology has wide-ranging applications in terms of the assessment of the impact of grazing animals on particular ecosystems or the quantification of nutrient supply to the animal from different selection choices.

Effects of dairy cow diet forage proportion on duodenal nutrient supply and urinary purine derivative excretion.

Four mature Holstein-Friesian dairy cows were used in a 4 x 4 Latin square change-over design experiment made up of four 4-wk periods to investigate the relationship between microbial protein flow to the duodenum and excretion of purine derivatives (PD) in the urine. Four dietary treatments based on ad libitum access to ryegrass silage were offered, with a standard dairy concentrate included at different forage:concentrate (F:C) ratios, calculated on a dry matter basis: 80:20, 65:35, 50:50, and 35:65. Feed intakes increased as the proportion of concentrate in the diet increased, despite a concurrent decrease in silage intake. Increased feed intake led to increased nutrient flow to the duodenum. Milk yields increased as the diet F:C ratio decreased, with cows offered the 35:65 diet yielding nearly 8 kg/d more milk than cows offered the 80:20 diet; the concentrations of milk fat decreased and milk protein increased with a decreasing F:C ratio. Purine derivative excretion in the urine increased with an increasing proportion of concentrate in the diet, and there was a strong linear relationship between total PD excretion (allantoin and uric acid) and microbial N flow to the duodenum: microbial N (g/d) = 19.9 + 0.689 x total PD (mmol/d); R = 0.887. This strengthens the case for using PD excretion as a noninvasive marker of microbial protein flow from the rumen in dairy cows.

Can live weight be used as a proxy for enteric methane emissions from pasture-fed sheep?

To test the hypothesis that sheep live weight (LW) could be used to improve enteric methane (CH4) emission calculations, mature ewes of 4 different breeds representative of the UK sheep industry were studied: Welsh Mountain, Scottish Blackface, Welsh Mule and Texel (n = 8 per breed). The ewes were housed and offered ad libitum access to fresh cut pasture of three different types, varying in digestibility: (a) a relatively high digestibility monoculture of perennial ryegrass (Lolium perenne), (b) a medium digestibility permanent pasture comprising a range of grass species, and (c) a relatively low digestibility native grassland pasture comprising mainly Molinia caerulea. Individual LW, feed dry matter intake (DMI), and CH4 emissions in chambers were measured. The linear functional relationship between DMI and CH4 emissions was positive (r = 0.77) with little breed effect. The relationships between LW and DMI, and LW and CH4 emissions were also positive but weaker, regardless of pasture type. It is concluded that change to LW was a poor indicator of DMI and has limited value in the prediction of enteric CH4 emissions from mature ewes.

Effect of breed and pasture type on methane emissions from weaned lambs offered fresh forage.

To investigate the extent to which enteric methane (CH4) emissions from growing lambs are explained by simple body weight and diet characteristics, a 2 × 2 Latin square changeover design experiment was carried out using two sheep breeds and two fresh pasture types. Weaned lambs of two contrasting breed types were used: Welsh Mountain (WM, a small, hardy hill breed) and Welsh Mule × Texel (TexX, prime lamb) (n = 8 per breed). The lambs were zero-grazed on material cut from recently reseeded perennial ryegrass and extensively managed permanent pasture. In each experimental period, individual ad libitum dry matter intake (DMI) was determined indoors following an adaptation period of 2 weeks, and CH4 emissions were measured individually in open-circuit respiration chambers over a period of 3 days. Although total daily CH4 emissions were lower for the WM lambs than for the TexX lambs (13·3 v. 15·7 g/day, respectively) when offered fresh forage, the yield of CH4 per unit DMI was similar for the two breed types (16·4 v. 17·7 g CH4/kg DMI). Total output of CH4 per day was higher when lambs were offered ryegrass compared with permanent pasture (16·1 v. 12·9 g/day, respectively), which was probably driven by differences in DMI (986 v. 732 g/day). Methane emissions per unit DMI (16·4 v. 17·7 g CH4/kg DMI) and proportion of gross energy intake excreted as CH4 (0·052 v. 0·056 MJ/MJ) were both higher on the permanent pasture. No forage × breed type interactions were identified. The results indicate that forage type had a greater impact than breed type on CH4 emissions from growing weaned lambs. It can be concluded that when calculating CH4 emissions for inventory purposes, it is more important to know what forages growing lambs are consuming than to know what breeds they are.